1. Field of the Invention
The present invention relates to heat exchangers generally and particularly to concentric heat exchanger having one media flowing internally within the heat exchanger and another heat transfer media flowing externally therethrough.
2. Description of the Related Art
There are a variety of heat exchangers using various designs of heat transfer surfaces. Air-cooled heat exchangers are known which consist of a bundle of smooth or finned tubes through which process fluid flows and is cooled by air blown over the tubes.
Shell-and-tube type heat exchangers are known which contain a number of tubes (smooth or finned) that are contained within a shell. Heat transfer tubes are placed between one fluid flowing inside the tubes with another fluid flowing outside the tubes and contained by the shell.
Plate heat exchangers consist of a series of parallel plates that are corrugated both to increase heat transfer and to give mechanical rigidity. They normally have flow paths in all four corners and are clamped together in a frame that has nozzles for line up with the plate ports. The nozzles are connected to external pipes that cover the two-fluid stream.
None of the above described heat exchangers have the strength and increased heat transfer characteristics of bulge formed heat exchanger surfaces.
The technique for forming such surfaces is known. One such hydraulic expansion technique is described in U.S. Pat. No. 4,295,255. Another method or technique is described in U.S. Pat. No. 5,138,765 as being used only on the internal surface of the flow channel. The specific application of the above hydraulic-expansion technique is applied to a stored chemical energy propulsion system. Therein the heat transfer effectiveness is improved both on the internal surface and is further enhanced by the flow channels. Strength is provided by a plate having the formed flow channels which are not bulge formed while the cover plate is bulge formed to provide added heat transfer surface and induce turbulent flow for increased heat transfer.
To date there are no known cylindrical heat exchangers that have hydraulically expanded or bulge formed flow channels on either one side or both sides of the heat transfer surfaces to provide strength and turbulent flow around these surfaces to increase heat transfer thereby. Clearly such designs are needed and would be beneficial to the art.